Under the Asylum Act, the placement of asylum seekers in detention cannot be based on the application for international protection alone, and can only occur on grounds of:
- National security, public order, public health; or
- Risk of absconding;
And be based on an individual assessment and if the effective application of less severe alternative measures is not possible.
The possible grounds for the detention of asylum seekers also include: 
- Applying for asylum at the border;
- Applying for asylum following a decision of removal from national territory; or
- The application of the Dublin procedure.
According to the law, detention may only be applied if it is not possible to effectively implement less severe alternative measures.
Moreover, Article 26(1) of the Asylum Act determines that asylum seekers who applied for asylum at the border remain in the international area of the (air)port while waiting for the decision.
As mentioned in General, systematic detention of asylum seekers in Portugal has been applied within the context of border procedures in which asylum seekers are detained until their application is admitted to the procedure (7 days) or for a maximum of 60 days in case of an appeal against the rejection of the application. Since March 2020, the border procedure has not been applied. Persons applying for international protection at the border were given entry into national territory, referred to the provision of reception conditions if needed and their cases were processed accordingly. At the time of writing, it was not clear whether this is temporary or will become permanent practice. Nevertheless, the border procedure is provided in national law and was systematically applied along with detention at the border until March 2020.
Asylum seekers who apply for asylum in detention at a CIT due to a removal procedure will also usually remain in detention during the asylum procedure until their application is admitted to the procedure (10 days) or for a maximum of 60 days in case of an appeal against the rejection of the asylum application. While the Asylum Act provides for the suspension of all administrative and/or criminal procedures related to the irregular entry of the asylum applicant on the national territory – and thus requires that the competent authorities are informed of the asylum application within 5 days for that purpose –  detention at a CIT due to a removal procedure will rarely, if ever, be suspended ex officio by the Criminal Courts on that basis. Detention within this context continued to be applied throughout 2020 (including in the detention centre at Faro airport).
CPR is unaware of case law relating to or judicial interpretations of detention grounds such as the application of a Dublin procedure, threat to national security, public order, public health, or risk of absconding.
 Article 35-A(1) Asylum Act.
 Article 35-A(2) Asylum Act.
 Article 35-A(3) Asylum Act.
 It is our understanding that while this article seems to provide for the general detention of asylum seekers within the context of border procedures, it must be applied with due regard for the rules established in Art.35-A of the Asylum Act.
 Article 26(4) Asylum Act.
 Article 35-B(1) Asylum Act.
 Article 33-A(5) Asylum Act.
 Article 35-B(1) Asylum Act.
 Article 12(1) and (3) Asylum Act.