He also isn't giving into the U.N., which a year ago had one of its panels dealing with drug issues calling for Bolivia and Peru to criminalize all use of the coca leaf, including drinking tea. This is change that didn't happen overnight. But coca has been a part of Bolivia's indigenous culture for centuries.

The constitution also provides greater access to health care and educational benefits and highlights community justice. Note, that's not vigilantism as the LA Times article linked above suggests, but a policy that stresses reconciliation and rehabilitation.

Community justice “in its traditional form in indigenous Andean villages...emphasizes reconciliation and rehabilitation," explains Daniel Goldstein, Director of the Center for Latin American Studies at Rutgers University, who has researched the topic extensively in Bolivia over a decade. "Rather than violent torture and execution, community justice promotes the 'reeducation' of community members who violate collective norms and rules, and the reincorporation of these offenders back into the community.”

In the eyes of its supporters, it is a move toward using dialog, community service work, and the restoration of harmony as a basis for dealing with conflicts. In other words, if you steal your neighbor's cow you might be required to help lay bricks for a school as opposed to being turned over to police and prosecutors many miles away.

Here is the Bolivian Presidency website. The only text I could find of the new Constitution is here (pdf), in Spanish.
As to what it says about coca:

El Estado protege a la coca originaria y ancestral como patrimonio cultural, recurso natural renovable de la biodiversidad de Bolivia, y como factor de cohesión social; en su estado natural no es estupefaciente. La revalorización, producción, comercialización e industrialización se regirá mediante la ley.

Via a free language translation service:

The State protects the ancient and native coca as cultural patrimony, renewable natural resource of the biodiversity of Bolivia, and
like factor of social cohesion; in its natural state is not narcotic. The revaluation, production, commercialization and
industrialization will be governed by means of the law.

Shorter version: Coca is an issue of cultural patrimony, not a narcotic and therefore okay.