What do you mean by: go through an instant exchange?
Exchange alt to bitcoin to use with LN across Europe. If you want to withdraw via LN like Binance, find here for DEX, instant btc><alts exchange that supports bitcoin LN.
https://cointastical.github.io/Exchanges-With-LN/I don't think European regulations can prevent you from withdrawing Bitcoin LN via DEX.
Not only state laws cannot stop decentralized exchanges, and I cannot judge whether this is prohibited or not. Europe has very strict tax laws, and a problem arises when legalizing cryptocurrencies, because decentralized exchanges do not provide documents on trading. Therefore, for the tax authorities, all cryptocurrency will be considered net profit when calculating fines.