It's a ruling on a legal technicality, that's all. They have been imposing restrictions using fast-tracked executive orders, rather than running through the full parliamentary process. The government have 30 days to get the rules through parliament.
This is
not a 'the-human-right-to-go-to-the-shops-is-more-important-than-the-human-right-to-be-alive' ruling. Because obviously no sensible court would rule in that way, because the idea is utterly insane.
For months, the Belgian federal government has used emergency executive orders to impose restrictions effectively bypassing the parliament. The government proposed a new "pandemic law" at the end of February to underpin its rules, but the law still needs approval from parliament.
https://www.politico.eu/article/belgian-court-slaps-down-covid-19-measures-reports/