Schengen Tourist Visa First port of entry

[p_surish]

Hi,

My parents have applied for Schengen Tourist Visa from Switzerland embassy in Mumbai. Now they are planning to visit Paris without going to Switzerland, can their first port of entry be France or do they need to enter Switzerland first and then to France ?

will there be any Port of entry problem if they enter France. Please help me they have already brought the flight tickets to Paris.