Investment Treaty Arbitration in 2026: States as the Client

Sartori & Partners data show that in investment treaty arbitration the state is the client more often than any single industry: government and public sector clients appear on 38.6% of the speciality's matters over three years. For firms that hire investment treaty arbitration lawyers, that sets the first question to ask of any candidate: how much of their record was built acting for states and public bodies, and how much for investors. The rest of the picture follows from it. The work is almost entirely contentious, hiring has picked up faster than in the parent practice, the bench is senior, and the lawyers who do this work rarely change city.

Over three years the speciality counts 127 matters on record, and government and public sector clients appear in 49 of them. No other client industry is large enough to stand beside that group. The type of work is just as concentrated: disputes and investigations account for 125 of the 127 matters, or 98.4%. Investor-state claims are brought by a foreign investor against a host state under a treaty, so the state sits on one side of every case; these figures say how often the firms on record were acting for it.

The flow of work is steady rather than occasional: 52 matters fall in the last 12 months. For a firm building or adding to this practice, the consequence is practical. State-side experience is the credential to test in the first interview, and conflict checks against sovereign and public clients belong at the start of a lateral process, before the offer, because a candidate's book can block a firm's existing investor work.

In the Sartori & Partners lateral database, hiring in the speciality rose 43.5% over the latest settled 12 months, from 46 to 66 moves. Over the same windows the international arbitration and public international law practice held flat (+12.8%), from 149 to 168, and the whole market rose 9.0%. The speciality is a large part of its parent: investment treaty work accounted for 38.3% of the practice's moves over 12 months, so a shift here shows up across the practice.

The yearly series puts the rise in context. The speciality recorded 46 moves in 2025, its low point, after 65 in 2024, and 2026 has already reached 57 with November and December still to come. Read that way, the increase brings hiring back to the pace of 2022 to 2024 after a quiet year. Over 12 months 39 firms made at least one hire in the speciality. A firm that held back in 2025 now competes for candidates in a market moving faster than its parent practice.

This is a senior market. Partners were 38.5% of the speciality's moves over 12 months and counsel 26.2%, against 35.8% and 16.7% in the parent practice and 27.7% and 12.7% across the market. Associates made up 35.4% of moves, against 58.5% market-wide. The counsel figure rests on a small base and is a rough size, but it stands well clear of both comparisons.

Movers also step up a title more often than elsewhere: 21.5% joined at a higher title than the one they left, against 16.7% in the practice and 12.9% in the market. Growing the bench from within is slow. Over 5 years the median lawyer promoted to partner in the speciality had 10.0 years of practice behind them, and only 21.3% made it within 8 years. A firm that needs state-side capacity this year will pay for it at counsel and partner level, and should be ready to offer the step up in title that movers here receive more often than elsewhere.

London took 38.5% of the speciality's moves over 12 months. Its index against the market is 417, above the parent practice's 307, which is already heavily weighted to London. Over three years Sartori & Partners figures put London at 33.0%, Paris at 13.1% and New York at 11.9%; in the practice, Paris and New York each took 7.8%.

The lawyers stay where they are. Only 11.3% of the speciality's movers changed city over 12 months, against 24.8% in the practice and 20.5% in the market. Over three years the figure is 19.3%, still below the practice's 26.1%. Teams count for more here than in most markets: 10.8% of moves came as part of a team joining the same firm, against 1.5% across the market. A firm opening a seat away from London, Paris or New York should plan to hire locally or bring a team, not count on a relocation.

Firms of 1,000+ lawyers took 72.3% of the speciality's moves over 12 months, close to the parent practice's 71.4% and well above the market's 53.6%. Firms of 400-999 lawyers took 21.5%. Over three years the picture holds: 66.5% went to firms of 1,000+ lawyers, against 52.5% across the market, while firms of 150-399 lawyers took 8.5% and firms under 150 lawyers 3.4%. Those last two are rough sizes on small counts. A firm below the largest size class competes for the same small pool of candidates, and should lead with the state-side and treaty mandates it can offer rather than with scale.

Start with the client. With government and public sector clients on 38.6% of matters, a lateral candidate's value depends on which side of the table their experience sits, and the conflict picture should be mapped before the first serious conversation. Budget for seniority: counsel and partners together were 64.7% of 12-month moves, so this is not a market to fill with associates and train up quickly. Recruit where the lawyers already are, mainly London, then Paris and New York, because few of them move cities. Move now rather than next year: hiring rose 43.5% in the latest settled window while the parent practice held flat (+12.8%), so the firms that already hire here are adding to their benches now.