In scriptures 8 types of marriages are described.
Manu Smriti 3.21. (They are) the rite of Brahman (Brahma), that of the gods (Daiva), that of the Rishis (Arsha), that of Pragapati (Pragapatya), that of the Asuras (Asura), that of the Gandharvas (Gandharva), that of the Rhashasas (Rakshasa), and that of the Pisakas (Paisaka)
Also, the following verses describe which marriages are suitable for which Varnas.
3.23. One may know that the first six according to the order (followed above) are lawful for a Brahmana, the four last for a Kshatriya, and the same four, excepting the Rakshasa rite, for a Vaisya and a Sudra.
3.24. The sages state that the first four are approved (in the case) of a Brahmana, one, the Rakshasa (rite in the case) of a Kshatriya, and the Asura (marriage in that) of a Vaisya and of a Sudra.
And, in general,
3.25. But in these (Institutes of the sacred law) three of the five (last) are declared to be lawful and two unlawful; the Paisaka and the Asura (rites) must never be used
Now,
Gandharva marriage:
3.32. The voluntary union of a maiden and her lover one must know (to be) the Gandharva rite, which springs from desire and has sexual intercourse for its purpose.
Rakshasha marriage:
3.33. The forcible abduction of a maiden from her home, while she cries out and weeps, after (her kinsmen) have been slain or wounded and (their houses) broken open, is called the Rakshasa rite.
Pishacha marriage:
3.34. When (a man) by stealth seduces a girl who is sleeping, intoxicated, or disordered in intellect, that is the eighth, the most base and sinful rite of the Pisakas.
So, when both the bride and bridegroom have no problems in marrying, that marriage comes under the Gandharva Rite. This one is acceptable even if kidnapping is involved.
However, the Rakshasa and Pisacha rites, where marriage takes place without the approval of the maiden and with force or stealth being involved, are generally considered as blameable forms of marriages.
For Kshatriyas, however, the Rakshasa marriage is approved as you can see from one of the verses given above.