The letter is the latest in a series of moves by the Iraqi Oil Ministry to try to control oil revenues from the Kurdistan region.
And the message, which was quoted by Reuters news agency, excerpts from, stated that "firm legal measures will be taken against all concerned parties, in order to prevent the loading of those illegal shipments coming from Iraq, including but not limited to shipments coming from the Kurdistan region."
"The Iraqi Federal Ministry of Oil and SOMO as its subsidiary reserve the right to take all legal measures against any dealer or buyer of smuggled crude oil who is proven to have loaded Iraqi oil from Turkey's Ceyhan Oil Terminal, specifically, without express endorsement from SOMO," SOMO added.
This move mimics a similar move by the Iraqi Oil Ministry in 2014 to prevent ships carrying crude from the Kurdistan region from unloading cargo at foreign ports.
A ruling by Iraq's Federal Supreme Court in February considered the legal foundations for the oil and gas sector in the Kurdistan region unconstitutional.
The Kurdistan Regional Government has repeatedly rejected the ruling. The region's prime minister last month described its decision as a "political" and unconstitutional ruling.
Iraq made several attempts to implement the Federal Court ruling. He summoned many companies operating in Kurdistan to commercial court sessions, which were repeatedly postponed, and introduced a policy to blacklist oil field service companies if they did not withdraw from the Kurdistan region.
The oil dispute between the two parties was renewed at the peak of prices and at a time when Iraq was seeking to increase its production and develop the oil infrastructure.
In May, the Iraqi Oil Ministry asked oil and gas companies operating in the Kurdistan region to sign new contracts with "SOMO" instead of the regional government.
Prior to that, Oil Minister Ihsan Abdul-Jabbar said that the Oil Ministry would start implementing the Federal Court ruling after talks with the KRG failed.
The oil file and the management of oil wealth is considered one of the most prominent outstanding issues between Baghdad and Erbil for years, and the events of 2017 reflected the state of tension between the two parties, forcing the federal government to send military forces that regained control of the oil fields in Kirkuk and forced the Kurdish forces to leave after a referendum on the independence of the Kurdish region The majority voted for secession.