In a private hearing days before the club was eventually sold to lifelong fan Simon Sadler, Justice Marcus Smith said the loophole was a "potential deal-breaker".
The judgement, which has now been made public, also reveals:? a last-minute fourth bid for the club was worth more than Sadler's;? the new owner won over the receivers with his plans for an academy and to invest in the stadium, pitch and training facilities;? and the club was facing "severe financial difficulties" if the sale had not gone ahead when it did.
Justice Smith, sitting in the High Court, was asked earlier this month to approve the sale - and, crucially, vary a previous order he made that could have allowed ousted former owner Oyston to claim ex-president Valerie Belokon's minority shareholding.
In a statement to the court, one of the receivers brought in to facilitate the sale, Paul Cooper, said all of the bidders told him "unequivocally" that they would not buy out majority shareholder Blackpool Football Club (Properties) Ltd - formerly Segesta - without also acquiring the 20 per cent share held by Belokon's VB Football Assets.
The sale was complicated by the fact that, in the event Oyston repaid the £25.7m owed to Belokon, Justice Smith's previous court order would have seen Oyston take control of the Latvian's shares.
In his ruling, Justice Smith said there were valid concerns that this could have been enforced even after any sale, adding that any buyer "would want an assurance that Mr Oyston will not pop up with an offer to pay whatever balance is due... at some future date and then demand the VBFA shares in return".
The issue was "an obstacle" to the sale, he added, and without the new owner being able to take control of Belokon's shares it was "unlikely the sale would go ahead at all".
In his evidence, Mr Cooper said: "(The bidders) are not prepared to have Mr Oyston as a partner in the football club".
Justice Smith approved the sale of the club to Sadler - citing the need for urgency to prevent the club facing "solvency difficulties" - and varied his earlier order to ensure Belokon's shares could be included in the sale, removing Oyston's potential future claim to them.
He said that even once the sale had been concluded Oyston would still be left owing Belokon "several millions".
Although none of the bidders were named in the court documents, they reveal Sadler's was the most thorough bid. He and his team spent more than 100 hours poring over club documents, including financial details.
The judge agreed the receivers "entirely correctly" identified him as the preferred bidder.
A second bid, for a "nominal amount" was made but the bidder had not carried out any due diligence at the time of the hearing.
A third bid, for slightly less than Sadler's, was received before the deadline but was complicated by the bidder's "interests in another football club", which could have led to problems with them being approved by the English Football League.
Fleetwood Town owner Andy Pilley is known to have had a serious interest in buying the club but has since denied making a formal offer to buy Blackpool.
In response to speculation that he was behind the third bid, he said he remained "committed" to Fleetwood Town.
A fourth bid - worth slightly more than Sadler's - was lodged 12 days after the May 25 deadline, by which point an exclusivity deal was already in place with Sadler.
Justice Smith said he agreed with the receivers' decision not to proceed with the bidder - who had no interest in acquiring Belokon's shares as part of the deal.
One of the reasons given was the "urgency" of the sale, with the club said to need "significant funds" before October to avoid falling into "severe financial difficulties".
Justice Smith said unspecified details uncovered by "desktop due dilligence" into the fourth bidder would have required "the most careful further due dilligence" were the receivers to proceed with a sale.