They are enforcing the sanctions on prohibited goods.
Lithuania Bans Transit Of Sanctioned Russian Goods To Kaliningrad (panic buying)
However you want to rationalize this, it is a provocation. The established rail corridors connecting Kaliningrad to Russia are being disrupted. The Russians can supply the territory by sea, so the only real purpose of this to poke the bear.
In a totally unrelated matter, the DC Council, with approval by Congress, changed the name in front of the Saudi Embassy to Khashoggi Way. There is no end to this stupidity. Another needless provocation.
Street outside Saudi Embassy in DC renamed Jamal Khashoggi Way