Jurgen Klopp was delighted Liverpool finally won the Premier League this season, because he fears any relaxing of spending rules may mark the end of honest competition in football.
The Liverpool manager worries that multi-billionaire club owners could overrun the game if restrictions are eased.
And he argued Monday was "not a good day" after Manchester City succeeded in their appeal against a two-year ban from Europe over alleged Financial Fair Play (FFP) breaches.
UEFA's FFP policy is facing fresh scrutiny after the Court of Arbitration for Sport (CAS), in assessing City's challenge to their punishment, determined that "most of the alleged breaches ... were either not established or time-barred".
Former Borussia Dortmund head coach Klopp said: "I'm not worried for Liverpool. I'm really happy we won the championship this year because it will not be easy in future if something changes.
"I like FFP because it gives us a frame. I've no idea how it exactly works but how I understand it, it gives us a frame in which we all have to work and I’m fine with that.
"If that means now we have to change that, then the future will show what it will mean exactly. For the football we know at the moment it was not a good day.
"It was not a day we all should celebrate and say, 'Oh, from now on everyone can spend as much as they want'."
He expressed the worry that any loosening of the limits clubs operate under would mean "there will be people with a lot of money who will be very, very influential".
City strenuously denied wrongdoing throughout as UEFA investigated their finances, while European football's governing body defended the FFP system after the CAS verdict was delivered.
UEFA said FFP had "played a significant role in protecting clubs and helping them become financially sustainable".
Klopp stressed his opinion was nothing personal against City, the team who will finish second to his Liverpool in the Premier League this season, a reversal on last season's positions.
The CAS ruling may even help Liverpool in their Premier League title defence, because City will not benefit from free midweeks between domestic games.
"I'm happy that City can play Champions League," Klopp said. "I don't want them to lose money or whatever, but if there are rules I think it makes sense that we all stick to it and not only some."