What are some post-colonial themes in "Passport" by Mahmoud Darwish? How can post-colonialism be applied to this poem?

This is a poem about conflict over identity. This conflict arises when one group, defined here as an outside/anterior group that has claimed local authority, attempts to take ownership of another group's right to self-definition. 

The speaker of the poem implies that his identity is not open to debate because, like the trees and valleys, his identity is a quality beyond the whimsy of policy.

"Don't ask the trees for their names
Don't ask the valleys who their mother is
From my forehead bursts the sward of light
And from my hand springs the water of the river
All the hearts of the people are my identity"

A conflict over self-definition falls squarely into the purview of post-colonial theory, which is interested in the cultural and intellectual ramifications of an occupying authorial force affecting the identity of a native or subjected population. When the colonial group defines the native group according to its own agenda, the colonial/colonizing group is presented as the positive side of a binary value system. 

Frantz Fanon, in particular, codified this behavior as a marker of colonialism in his critical work, which is now central to the canon of post-colonial theory. Fanon suggested that colonizing groups succeeded in turning native populations against themselves internally, forcing them to adopt a value system that deemed them as possessing an inferior identity in comparison to the group in power. 

"One way colonialism achieved this end had been to plant, and then constantly to reinforce, a feeling of inferiority in the mind of the colonized."

In the Darwish poem, we see the right to self-definition being challenged by the colonizing group. The speaker resists and cries out against the theft of his right to define himself. 

The poem's intentions are essentially political in ways that align it with post-colonial literature. The poem's resistance to a loss of authority over self-definition is critical to its message. The poet questions the nature of what he is being forced to do by giving up his passport.

"Stripped of my name and identity?"

More than a loss of mobility that comes with having no passport, the speaker feels that the validity of his identity is being undermined. 

The question of rights raised here is not a purely intellectual question about the esoteric notion of identity. As complex as identity is, as a psychological concept, there is a fundamentally political aspect involved in identity. The politics co-mingle with some of the deeper issues of identity and generate a troubling, schismatic dynamic. 

While it is possible to protest the act of being stripped of a passport, it is more difficult to protest the more ephemeral but deeply felt connotations of the act. 

The limits on the ability to protest on a philosophical level are explored in other post-colonial texts like Things Fall Apart and Waiting for the Barbarians, where we see characters struggle to effectively achieve an internal and integral bulwark against a colonial value system.