Two controversial laws signed by the Bosnian Serb president, which Washington says undermine the peace deal that ended Bosnia's 1990s war, entered into force on Sunday.
Kremlin ally President Milorad Dodik had on Friday signed legislation into law that effectively allow the Bosnian Serb entity to bypass or ignore decisions made by the top international envoy to Bosnia.
The latter, currently German diplomat Christian Schmidt, oversees the civilian aspects of the Dayton peace deal that ended the 1992-1995 war.
The international envoy has important executive powers notably to sack elected officials and impose laws.
A second piece of legislation signed into law by Dodik on Friday suspends the Bosnian Serb entity's recognition of rulings made by Bosnia's constitutional court.
On Sunday, both bills, that were approved by Bosnian Serb lawmakers last month, officially entered into force with their publication in the official gazette of Republika Srpska (RS).
The RS along with the Muslim-Croat Federation makes up post-war Bosnia.
The two semi-autonomous entities are linked by a weak central government.
The Bosnian Serb entity's initiatives had provoked strong reactions particularly from Bosnian Muslim leaders, and have also been criticized by Washington, Paris and Berlin.
US Secretary of State Antony Blinken on Saturday tweeted that Dodik's signing of a law rejecting the international envoy authority "violates the Bosnia and Herzegovina constitution and undermines the Dayton Accords."
Dodik signed the bills just days after Schmidt tried to head off the controversial moves by passing an executive order that deems them illegal and prevents their implementation.
Schmidt made the ruling last weekend when he also passed a new measure that would allow Bosnia's judiciary to prosecute politicians who oppose his orders and those of the constitutional court — with punishments running up to five years in jail.
Dodik has refused to recognize Schmidt's authority since the position lost the backing of the United Nations thanks to an intervention by Russia and Beijing.
Dodik — who remains a Moscow ally — has held enormous sway over the Bosnian Serb entity for years, repeatedly stoking ethnic tensions with his secessionist threats.
Earlier this week, Dodik vowed to continue to oppose the envoy.