The edict directly from President Muhammadu Buhari's office appeared to be part of a campaign pledge to crack down on oil industry corruption and theft.
But the disarray it has caused, even three weeks on, underscores the problems Buhari faces in trying, as an oil industry outsider, to tackle problems in the sector head on.
"It's a mess," one trader said of the ban. "Nobody knows anything concrete."
Buhari has kept the oil portfolio for himself for now, and said that he would not appoint ministers until September. Last month, he announced plans to cleave state oil firm NNPC in two, though details are vague, and sacked the chiefs of the Navy and the Nigerian Maritime Administration and Safety Agency (NIMASA) - agencies that would help enforce the ban.
Some warn the ban could hurt the country's near-term oil revenue more than the thieves it aims to stop.
"In the end, it's going to make a much bigger problem for Nigeria than tanker owners," said Ehsan Ul-Haq, senior market consultant with KBC Energy.
Traders are still struggling to get to grips with the list of tankers, which sources said is haphazard and confusing; while the headline number is 113 vessels, at least nine are listed twice, and shipping sources said one was scrapped in 2012.
Of the others, many have not called at Nigerian ports in years, if at all.
"The whole list stinks if a lot haven't been to Nigeria for a long time," one Nigeria-based oil industry executive said.
An NNPC spokesman and the head of crude marketing did not respond to several requests for comment. The presidency confirmed it had sent the list to NNPC but declined to elaborate on the rationale for vessels included.
Inside and outside Nigeria the origin of the list seemed to be in a locked box inside the president's inner circle, and NNPC itself appeared only to have limited information. Oil traders who asked NNPC officials directly for answers said their attempts had borne little fruit.
CLAWING BACK STOLEN OIL
Oil theft is rampant in Nigeria; the country has estimated losses at as much as $35 million per day - roughly a quarter of its gross domestic product.
Buhari has vowed to recover the "mind-boggling" amounts of stolen oil money, enlisting help from the United States.
The theft comes at various points - siphoned from pipelines, diverted from loaded vessels and via paper accounting fraud.
Much of the stolen physical oil, country observers say, ends up on very large crude carriers (VLCCs) like those now banned.
Some said the ban could be a shot across the bow at those engaged in illegal activities or who look the other way when it happens involving their ships.
"What NNPC appears to be doing is attempting to get vessel owners to be more proactive in ensuring their vessels are used only for legal business," one trader said, noting this is an important goal for the country.
The source added, however: "It's a fairly blunt instrument."
The confusion has sparked concerns that more tankers could be added to the list. As a result, some could avoid Nigerian ports altogether, while others could demand higher rates to call there.
Some traders are also pressing for lower official selling prices from NNPC to compensate for any difficulty the ban creates; if successful, this would hit Nigeria's already battered revenue even harder.
"Nigerian grades have already been suffering ... this will increase their pain," Ul Haq said, noting the global excess of crude. "They will soon realise this is not the right way of dealing with oil theft."