What Are the Regulatory Concerns Surrounding the Use of ‘Last Look’ in Financial Markets?

Regulators are concerned that 'last look' can be unfairly used to reject trades based on adverse price movements after the client has committed, which can be seen as a form of predatory behavior. Concerns include information leakage, unequal access to market data, and the potential for LPs to selectively accept only profitable trades, leading to poor execution quality for the client.