Key facts of the case - A Non Profit Organisation owning a building asked for total tax exemption because of the exercise of public worship, teaching and voluntary work inside.
The Belgian state granted only a partial exemption because of the presence in the building of a meeting room and a room for children where the worship, teaching and voluntary work could not be exercised.

Main reasoning of the Court - The Court of cassation held that immunity from taxation (Article 8 of the tax income code) was limited to the part of a building that is regularly assigned to the exercise of public worship, teaching or voluntary work.
In other words, the exercise of public worship could not be organized without the building or any part of it.
In this case, the meeting and children rooms have not a necessary relation between these rooms and the real exercise of worship or teaching activities because the appellant could not prove this necessary relation.