Bulgarian lawmakers this week banned hydraulic fracturing, known also as fracking. The measure calls for a $65 million fine for violations of the law.
Poland has some of the richest shale gas deposits in Europe. Bulgarian officials last year said there was enough shale gas in that country to meet energy demands into the foreseeable future.
The Polish government said it wasn't deterred by the Bulgarian measure.
"This will not change Poland's existing position presented to the EU, in which every member state has the sovereign right to define its own position regarding energy resources," the Polish Foreign Ministry said in a statement published by the Sofia News Agency.
In June, Chevron won the rights to explore for shale in Bulgaria. The Polish government said companies like Exxon Mobil and Chevron were examining shale deposits in the country, though protests against shale have occurred there.
Critics of hydraulic fracturing note chemicals used in hydraulic fracturing fluid could contaminate groundwater.