Apparently the citizen did not have any gun with him.
But if he had, and it was securely in the trunk, then he would have been protected when traveling interstate by Federal statute, no matter what Maryland’s laws are.
As for SC, they issue carry permits only to SC residents or property-owners. They do not honor other state’s carry permits.
NJ and MD, and parts of southeastern NY, and MA, do not in practice issue carry permits. I know NJ best: they have a procedure on the books, but in practice do not issue carry permits to ordinary citizens. They require that you have evidence ahead of time that you (as an individual) are under some direct threat, specific threat. Then they may take up to six months to issue a permit. They evade the 2nd Amendment, and ignore recent Federal court rulings on this issue, and get away with it because those rulings were not made in the Federal District to which NJ belongs.
If the Federal courts do not get throughly packed with 0’s appointees, it is possible that the courts will eventually rule against NJ.
NJ is generally a lawless state, anyway: it is ruled by its own politicized courts, who make up their own rules by fiat. We need a new state constitution here in the Garden State! But that would probably be of no use, because the state is virtually broke, and would not have the money to print copies of the new constitution.
South Carolina Reciprocity
RECIPROCITY
Alaska, Arizona, Arkansas, Florida, Idaho (Enhanced Only), Kansas, Kentucky, Louisiana, Michigan, Missouri, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, Texas, Tennessee, Virginia, West Virginia, and Wyoming.
Residents of reciprocal states who hold permits issued by their states of residence may carry concealed firearms in South Carolina, but must abide by the restrictions in the South Carolina CWP law. For that reason, out of state residents of reciprocal states should familiarize themselves with restricted carry locations and other provisions of South Carolina law posted on this website. South Carolina permittees who carry firearms in reciprocal states are likewise responsible for familiarizing themselves with the applicable laws and regulations of the reciprocal state. Web sites of those states may be accessed by selecting the desired state name listed above.
http://www.sled.sc.gov/Reciprocity1.aspx