From his press release (link):

In response to the Mexican government’s efforts to "bully" the people of Oklahoma through a trade war, (Oklahoma) state Rep. Randy Terrill today called for imposing "much tougher sanctions on illegal aliens."

"This represents an attempt by a foreign nation to interfere with the sovereign actions of a U.S. state," said Terrill, R-Moore. "We clearly not only have the right, but the responsibility to legislate for the public health, safety, morals and welfare of our citizens – not theirs.

...This week the Mexican House of Representatives passed a resolution denouncing U.S. states that impose remittance taxes and calling upon the Mexican government to take trade measures against those states.

The resolution specifically targets Oklahoma, saying remittance legislation enacted in this state is an "immoral, abusive and harmful" act against "immigrants’ rights."

The rest is all good, including him offering Mexico to help create jobs in their country in order to improve both countries' lots.