This requires prayerful reflection and a lot of basic honesty.
If both the bride and groom are Catholic, then - of course - they celebrate their marriage at a Nuptial Mass. But the decision to celebrate an ecumenical or "mixed" marriage (where one party is Catholic and the other is a practicing non-Roman Christian or non-baptized) with the Nuptial Mass has to take into consideration those from other denominations who would not be familiar with the Catholic Mass and who would not be able to receive holy communion.
In another case, if the majority of those who will attend are un-churched or attend church very rarely, the celebration of the Eucharistic liturgy may not be meaningful for them. In such instances that which should be a powerful sign of unity around the one table can unintentionally highlight the pain of division that exists in the Christian community.
The option to celebrate a marriage with a Nuptial Mass is never absolutely denied simply because one party is not a Catholic. But ecumenical marriages are generally celebrated without the Nuptial Mass. It's a delicate question with which to wrestle, and that's why it demands prayerful reflection, basic honesty, and an abundance of charity and sensitivity.