The Polish President Andrzej Duda has declared a state of emergency in Belarus because of the influx of migrants from the former Soviet state in parts of two border regions.
The September 2 ruling came at the request of his government earlier this week.
The emergency rules would prohibit demonstrations in a thin strip along the border and oblige people to carry ID.
It lasts 30 days but Duda could extend it.
About 3,000 migrants attempted to enter Poland from Belarus last month.
Poland and the EU believe that the illegal crossings are staged by the strong man Alyaksandr Lukashenka in order to get revenge for the sanctions against his authoritarian rule.
The EU has imposed several rounds of economic fines on members of the Lukashenka government, state-owned companies and business tycoons who have profited from his rule after brutally cracking down on demonstrators.
Migrants from Belarus have also entered Latvia and Lithuania, two other EU member states that border the country. Most of the migrants are from the Middle East, including Iraq and Afghanistan.
Poland started building a 2.5-meter-high fence along its 418-kilometer border with Belarus last week to slow the influx.
The state of emergency is the first in the post-communist history of Poland.