With one caviate, As long as the garrison remained as small as Major Anderson's was and did not recieve any additional reenforcements and depended upon the Charleston Authorities for their supplies.
Just as with President Andrew Jackson sending of additional United States soldier to Fort Moultrie during the 1832 Nullification Crisis. However in 1832 that forts guns were not pointed at Charleston itself and its people as the gun placed as a "mortar" was.
The South Carolina authorities had to be able to observe some of these improvements to Sumters warlike capabilities from Fort Moultrie with their naked eyes, let alone field glasses, and the visits of officials that went to Fort Sumter itself to deliver mail and negociations. And even for a period of time supplies. All of these things, as I have said, could only be taken as a threat to the people of Charleston and were intended to imply that same threat. And the 8 inch Columbiad gun placed as an indiscriminately aimed "mortar" in 1861 was a terror weapon, and intended as nothing else. It also makes a lie out of the assumption that the guns of Fort Sumter could not reach the city itself.
All of this would combine to be, in the minds of the people of South Carolina, as an Act of War. That there was no peaceful intent in the occupation of Fort Sumter by Major Robert Anderson. And would have been as welcome as a peaceful occupied part of the independent nation of South Carolina as Guantanamo Bay is to the President Fidel Castro and the government of Cuba. However, Guantanamo Bay does not control the entire commerce of the only major port of entry of Cuba.