The government will breach international principles of the role of lawyers if it blacklists law firms with links to electoral watchdog Bersih, says Lawyers for Liberty.

This is especially if it precludes firms whose lawyers have represented Bersih on matters from providing services to the government and government-linked companies.

Lawyers for Liberty executive director Eric Paulsen said it breaches the "cab-rank rule" and United Nations Basic Principles of the Role of Lawyers.