MEXICO CITY, Feb 17 (Reuters) - Mexico will put back into effect a controversial regulation that reduces the time period of permits to import and export oil and hydrocarbons, according to a document published on the National Commission for Regulatory Improvement's website on Thursday.

The document, which has yet to be published in the Official Gazette to enter into force, will overturn the suspension of a previous agreement, enacted in 2020, that reduced the maximum term of the permits to five years from 20 years.

Only those that have already obtained a legal measure will be able to evade suspension of the 2020 rule that shrank the length of the permits.

"It will be applicable to all those interested in importing and exporting the petroleum and hydrocarbon products regulated therein, with the exception of those subjects that have obtained a precautionary measure with particular effects against its application," according to the document.

Mexican President Andres Manuel Lopez Obrador has sought to reverse the opening of the energy sector carried out in the previous government. Lopez Obrador has said publicly that he considers it an obstacle for the activity of state-owned companies such as Petroleos Mexicanos (Pemex) and electricity generator CFE.

His government has made several provisions to reduce the presence of private companies in the energy market and favor Pemex and CFE, but most of those rules have been challenged or suspended in court.

The Mexican Congress is currently discussing a constitutional reform that seeks to give the CFE control over the electricity market, favor the dispatch of its energy, and eliminate generation permits to private companies. (Reporting by Adriana Barrera; Writing by Valentine Hilaire; Editing by Drazen Jorgic and Leslie Adler)