The winger was spotted in his homeland over the weekend, fuelling speculation he will join Manchester United this summer.
However, Dortmund's communications chief Sascha Fligge says there is no problem with Sancho being in England, so long as he returns for preseason training on August 10.
Fligge said: "It's common and fine for players to go home before a training camp if they're not risky.
"The same goes for Jadon [Sancho].
"From our point of view, the pictures that have been shown to us so far do not violate."