WESLACO – More changes may be coming to the Rio Grande Valley's landscape ahead of the possible arrival of the caravan.

CHANNEL 5 NEWS took a look at the acts that grant  the president the ability to make these changes.

National Guard, Border Patrol, and now active duty military forces – the troops are allowed to be here.

The Posse Comitatus Act of 1878 restricts their duties. 

Dr. William Green, a political science assistant professor at STC, explains the act which restricts the use of the military to just logistical support.

"They can be used for all these indirect assistance. So, they can operate equipment, military equipment. They can share information with Border Patrol, with customs agents. They can do aerial recognizance. The military can be involved in those things. They can transport Border Patrol," he said.

Key exceptions allow troops to be used for local law enforcement.

The Act states: "Pursuant to the presidential power to quell domestic violence, federal troops are expressly exempt from the prohibitions of Posse Comitatus Act, and this exemption applies equally to active-duty military and federalized National Guard troops."

The cities of Brownsville and McAllen each say they are monitoring ports of entry and will stay open until they're informed they should do otherwise.

Brownsville's City Manager's office sent the following statement:

"The City of Brownsville is in communication with U.S. Customs & Border Protection, Cameron County Office of Emergency Management, local police, fire, EMS, Office of Emergency Management and health officials to monitor the caravan. The City of Brownsville will maintain normal operations to provide a high quality of service to Brownsville residents."

McAllen City Manager Roel "Roy" Rodriguez sent the following statement:

"Right now, closing the bridge would be the absolutely last resort. CBP does not believe that will be necessary, however, they do have a contingency plan if that occurs.  Obviously, for the City of McAllen it is of monumental importance that the bridges remain open for commercial traffic and activity; however, CBP is our partner and we will work with them on this contingency."

The bridges may not be open for asylum seekers when they arrive; the president said he intends to block their entry.

It's a move made previously by the administration. 

"It seems like they're going to evoke the same rights as the travel ban," says Zone Nguyen, an attorney who has experience as a major and judge advocate in the U.S. Army Reserve.

He explained this act would need legal validation.

"In the Immigration and Nationality Act it says that you could ban if it would be contrary to national interest, it be detrimental to the interests of the U.S. Again, those interests would have to be national security, not political or anything else."

The administration would need to prove that this specific group of people poses a national security risk.

The Immigration and Nationality Act to prohibit entry to certain immigrants was used before from the Reagan Administration to, most recently, the Obama Administration. 

A Congressional Research Service report lists that in March of 2015, through an executive order, the Obama administration suspended entry to those who had "contributed to the situation in Venezuela." 

It included taking part in acts of violence, abusing human rights or engaging in actions or policies that undermined democratic processes or institutions.

In May of 2006, through a proclamation, the Bush Administration suspended entry for those responsible for threatening the transition into democracy for Belarus.