GPs may be forced to act as cross-border healthcare "gatekeepers", which might threaten their careers, the Medical and Dental Defence Union of Scotland (MDDUS) has warned.
It fears the possibility of "damned if you do, damned if you don't" situations resulting in disciplinary hearings or discrimination tribunals.
Concerns stem from an EU consultation on "patient mobility" that seeks to "ensure legal certainty" on cross-border healthcare.
MDDUS medicolegal adviser George Fernie said: "If GPs are expected to act as gatekeepers, we have a right to expect that they should neither fall foul of the NHS complaints procedure for alleged discrimination nor GMC guidance about deciding on access to medical care."
GMC guidance warns doctors not to discriminate against patients by allowing their "personal beliefs" to affect the treatment they provide or arrange. "Personal beliefs" explicitly includes views on ethnic or national origin, and economic status.
But under the EU proposals, if a GP believes that a patient effectively has no right to UK healthcare, that leaves them open to a charge of flouting GMC guidelines, and also breaching NHS contractual regulations.
The MDDUS wants to ensure doctors are not vulnerable if this policy is implemented